Which edition applies to your job right now
Right now, if you're replacing a gas or oil boiler in England, the rules your installer should be working to are the 2021 edition of Approved Document L, as amended in 2023. That's the edition behind the efficiency minimums, the control requirements and the sizing rules you'll find on a current quote.
A new edition of Approved Document L takes effect on 24 March 2027. Until that date arrives, the 2021 edition (with its 2023 amendments) is still the one to hold your quote against, even for a job being arranged close to the changeover.
Two editions, one date apart
Because the new edition starts on a fixed date, there's a period where two editions are both current. A job notified just before 24 March 2027 can end up following different rules from one notified a few weeks after. The changeover between them is set out in Circular 01/2026, the government's notice covering how the 2026 changes are brought in.
If your quote names an edition at all, check it says 2021, with the 2023 amendments, for work carried out before 24 March 2027. If it doesn't say, ask your installer which edition they're working to. For what changes once the new edition takes hold, the differences between the two editions are set out on their own.
What if the work spans the changeover
If your installer notifies the job to building control before 24 March 2027, it can still be carried out under the earlier rules, as long as the work starts before 24 March 2028. This is the changeover rule set out in Circular 01/2026.
What counts as notifying and starting
Notifying is the formal step where building control, or the installer's competent-person scheme, is told the job is going ahead. Starting is when work on site begins. Both dates matter here, not just one.
What this means for your quote
If you've had a quote drawn up now for work planned for next spring or later, ask your installer two things: when they expect to notify the job, and when they expect to start it. If both fall inside the changeover window, they can work to the edition that applies today. If the start date slips past 24 March 2028, the job falls under the 2026 edition instead, and the requirements on your quote may need to change with it.
Where the timetable is close to either date, it's worth asking what the installer would do if the start were delayed, and which edition they'd then be working to.
Dates to check in your quote and paperwork
Most replacement boiler jobs are still worked to the 2021 edition of Approved Document L, with its 2023 amendments. The 2026 edition takes over on 24 March 2027, and a handful of dates in your own paperwork tell you which one governs your job.
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The date work is due to start on site
If your installation starts before 24 March 2027, the 2021 edition applies. After that date, the 2026 edition is the default, unless the changeover rule below keeps you on the earlier one.
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The date your installer notifies building control
Notification can be submitted ahead of the work itself, so check this date separately from the start date on your quote.
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Whether your job falls under the changeover rule
Under Circular 01/2026, a job notified to building control before 24 March 2027 can still be built to the 2021 edition, but only if the work starts on site before 24 March 2028.
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The edition the job is done to
Ask the installer which edition of Approved Document L the job is being done to, and get the answer in writing.
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Whether your quote was priced against the right edition
A quote written now for work starting after 24 March 2027 should already reflect the 2026 edition's requirements. Ask your installer which edition they have priced to if the quote does not say.
If your job sits close to either date, the notification date and the start date together decide which edition applies.
Questions about the changeover
My installer's quote names the old edition of Approved Document L. Is that a problem?
Not necessarily. The 2021 edition, with its 2023 amendments, is what governs most boiler replacements at the moment, and it carries on applying to work that was notified to building control before 24 March 2027, as long as the work itself starts before 24 March 2028. That changeover is set out in Circular 01/2026. Ask the installer which edition they're working to, and when the job will be notified and when it's due to start, so you can check those dates against your own quote.
Why does my quote, or the document I was sent, still call it 'Conservation of fuel and power'?
Approved Document L Volume 1 used to be called 'Conservation of fuel and power' and is now titled 'Energy and greenhouse gas emissions'. If a document or a link you were sent still uses the old name, it was written before that change and could be the superseded edition. Ask the installer to confirm which edition the quote is working to by name and date.
I've got a quote now, but the job isn't booked in until next spring. Which edition applies?
What governs your job is not the date on the quote, it's when the work is notified to building control and when it starts. The 2021 edition, with its 2023 amendments, still applies to work notified before 24 March 2027, provided it starts before 24 March 2028. If your job is notified now but won't start until next spring, it's likely to fall under that earlier edition still, but ask the installer to confirm the planned notification and start dates and check them against those two cut-off dates yourself.
Does a new combi have to meet different requirements under the 2026 edition than it does now?
What a gas or oil boiler has to meet for efficiency and controls is set by Approved Document L, and some of the detail changes between the 2021 edition and the 2026 one. What Changed in the 2026 Edition of Approved Document L sets the two versions side by side, clause by clause, including anything specific to a combi. If your quote doesn't say which edition it's working to, ask the installer, because that's the only way to check the figure on your quote against the right requirement.
My quote doesn't mention an edition of Approved Document L at all. What should I do?
Ask the installer to add it before you accept the quote. A quote that names the edition it's working to gives you something to check the requirements against, while one that doesn't leaves you unable to tell whether it follows the current rules or an older set of them. What the Building Regulations Require of a Boiler Installation sets out what a quote should generally cover once you know which edition applies to your job.